Dozens of people were detained in two cities in largely Kurdish southeastern Turkey.
In Diyarbakir, the largest city in the region, more than 5,000 slogan-chanting demonstrators protested. Police did not initially react but charged when they were attacked with stones. Several dozen people were detained.
In a separate incident at Yuksekova, an isolated small town near the borders with Iraq and Iran, police used tear gas and water cannons to disperse a crowd of several thousand that had set up road blocks and burned tyres, the Anatolia news agency reported.
A car bomb which detonated during the protest injured a 28-year-old man, Anatolia said, adding police had launched an investigation into what type of explosive had been used.
It said police had made "numerous" arrests but gave no precise figure. Shops remained closed Saturday in the town, it said.
On Friday police and Kurdish demonstrators had clashed in Istanbul and other cities.
Police used water cannons to disperse Kurds in the Istanbul district of Umraniye, while in nearby Kucukcekmece petrol bombs damaged a shopping centre, Anatolia reported.
The pro-Kurd news agency Firat for its part said police quashed protests in the cities of Mersin, in the south, Sanliurfa in the southeast — where vehicles were set on fire — and Van and Varto in the east.
Ocalan’s lawyers had reported he had been assaulted by a guard and threatened with death in his island prison of Imrali, in the northwest, where he has been held in solitary confinement since 1999.
Similar reports in the past have stirred anger among Kurds who look on Ocalan, head of the separatist Kurdistan Workers’ Party, as a hero.
Arrested in Kenya in February 1999, he was sentenced to death by a Turkish court but the sentence was commuted to life imprisonment in 2002 after Turkey abolished the death penalty.
The PKK is blacklisted as a terrorist organisation by the European Union and the United States as well as by Turkey. Some 44,000 people have died since its conflict with the Turkish state began in 1984.